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Mental Accounting Explains Why You Buy Things You Don't Need

Would you drive 20 minutes out of your way to save $5 on a $15 calculator?

Would you drive the same distance to save $5 on a $125 leather jacket?

According to research from Richard Thaler at University of Chicago, 68% of respondents would drive to get the calculator but only 29% for the leather jacket. On the surface, this result is illogical – the savings is the same ($5) in both cases. The decision seems to be based on the inherent concept of getting a deal. One third off of an inexpensive calculator is a more powerful motivator than 4% of a leather jacket.

Thaler describes this irrational decision as an example of mental accounting. Mental accounting can be thought of as the home equivalent of financial accounting; both have charts of accounts, closing periods, and investment trade-offs. Unfortunately, while there are professional financial accountants, the evidence suggests that we’re not very good when it comes to mental accounting.

People mentally create spending accounts with implied budgets for activities like entertainment, food, travel, and clothing. If they feel like they’ve overspent in one category, they will delay needed purchases in that specific category – even though they still spend on other items. A Princeton study showed this effect by asking participants to react to the following scenarios:

Imagine you just arrived at a theater and as you reach into your pocket to pull out the $10 ticket you purchased in advance, you discover that it’s missing. Would you fork over another $10 to see the movie?

Compare that to a second scenario in which you did not buy the ticket in advance, but when you arrive at the theater, you discover you had lost a $10 bill on the way. Would you still buy a movie ticket?

Even though they have the same value, only 46% of those who lost the ticket were willing to buy a replacement, while 88% of those who lost the equivalent amount in cash were willing to buy a ticket. In the first case, the participants reported that they felt they were paying $20 for the movie because they were withdrawing additional money from their entertainment budget while in the other, the lost money came out of an overhead budget.

By contrast, at work we’re often willing to transfer budget from one category to another. For example, if your travel budget is down to zero but you need to visit an important client, it’s likely that you can use available funds from the third-party consulting budget instead. The impact on cash flow is the same.

Like financial accounting, mental accounting requires people to periodically close the books. As I’ve previously blogged, taxi drivers seem to balance their mental books on a daily basis. Hourly employees spend more on weekends, regardless of their actual account balances. Every year I spend less in the first two weeks of January and the last two weeks of April, even though I know holiday gift giving and tax paying won’t be repeated for another year.

While some believe that mental accounting is over-hyped, I find that it often explains seemingly irrational financial behavior. Like why I've bought so many calculators on sale...

As Chief Digital Officer at SAP, I'm responsible for driving growth and direction of SAP’s new digital business, which will help customers discover, buy, implement, use,…

As Chief Digital Officer at SAP, I'm responsible for driving growth and direction of SAP’s new digital business, which will help customers discover, buy, implement, use, and renew SAP offerings in a simple, entirely digital interaction. I was named the company’s first Chief Digital Officer in November 2014, after serving as its Chief Marketing Officer for three years. I am an active member of the enterprise applications community, a frequent speaker at industry events, and author of the blog (http://jonathanbecher.com). I joined SAP from its acquisition of Pilot Software where I was President and CEO. Prior to Pilot Software, I was interim CEO and president of Accrue Software; and president, CEO and co-founder of NeoVista Software. Earlier in my career, I held a variety of senior roles at MasPar Computer Corporation. I completed my Master of Science degree in computer science from Duke University and a Bachelor of Science degree in computer engineering from the University of Virginia. To see my latest thoughts, please refer to my recent activity feed.